Echocardiography in pregnant women
Gebelikte ekokardiyografinin yeri
Nurgül Keser
University of Maltepe, Istanbul, Turkey
Introduction
Despite continuous improvements in diagnostic cardiology techniques, echocardiography remains the cornerstone both for assessing the reversible physiological cardiac remodeling of pregnancy associated with changes in valve patency or trans-valvular flow pattern, which can best be assessed by the comp-lementary use of quantitative pulsed and continuous Doppler and qualitative color Doppler technology and for noninvasive cardiovascular assessment of the pregnant woman with heart disease or suspected cardiac abnormality (1).
Among the physiologic alterations during pregnancy incre-ase in cardiac output (CO) is the most prominent one. Hormonally mediated increases in blood volume, red cell mass and heart ra-te result in a major increase in CO during pregnancy (2). Cardiac output increases significantly at the early to mid third trimester and is maintained until term. Peak CO of 46-51% occurred from a 15% increase in heart rate and 24% increase in stroke volume (3). During labor and delivery, pain and uterine contractions re-sult in additional increases in CO(%20 with each contraction) and blood pressure. Immediately following delivery, relief of caval compression and autotransfusion from the emptied and
contrac-Address for Correspondence: Nurgül Keser, Professor of Cardiology, Mazharosman sok. Aziz Bey apt No:20/11 Feneryolu, Istanbul, Türkiye
Tel:+9 0 532 2149518, Fax:+9 0 216 3709719, E-mail: [email protected] N
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Beyond evaluating physiologic alterations encountered during pregnancy quantitative pulsed- and continuous Doppler and qualitative co-lor Doppler technology can be used for cardiovascular assessment of the pregnant woman with heart disease or suspected cardiac ab-normality. Echocardiography provides information about disease etiology, leads to accurate and non- invasive assessment of disease se-verity and is a powerful means of monitoring progression. Only with echocardiography it has been clearly demonstrated that during preg-nancy congenital heart disease is the first leading abnormality followed by rheumatic heart disease. Doppler and qualitative color Dopp-ler are useful to illuminate the pathophysiology of the hemodynamic consequences of fixed valve stenosis during pregnancy with respect to the labile nature of gradients resulting from variable loading conditions of pregnancy. Accurate cardiac diagnosis leads to accurate es-timation of prognosis, illuminates the necessity of noninvasive monitoring throughout pregnancy and labor, and leads to determine whet-her surgical or medical intervention should be performed. Need for Fetal echocardiography should also be considered after maternal ec-hocardiography is undertaken. Although there are no strictly defined limits established for the use of Doppler ultrasound in the early preg-nancy there is an unequivocal demand for carefulness that is best expressed by the ALARA principle,-as low as reasonably achievable. (Anadolu Kardiyol Derg 2006; 6: 169-73)
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Keeyy wwoorrddss:: Echocardiography, Doppler, pregnancy
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BSTRACTEkokardiyografinin gebelerde kullan›m› günümüzde gittikçe daha yayg›nl›k kazanmaktad›r. Yeni ekokardiyografi tekniklerinin eklenmesi ile sadece gebelik s›ras›nda oluflan fizyolojik de¤iflikliklerin izlenmesinde de¤il,olas› yada kan›tlanm›fl kalp hastal›¤› olan hamilelerin tespiti, kalp hastal›klar›n›n sebebinin ve a¤›rl›k derecesinin belirlenmesi ve ilerleme h›z›n›n takibinde de ekokardiyografi tart›fl›lmaz yere sahip ol-mufltur. Ekokardiyografi sayesinde gebelikteki kalp hastal›klar› aras›nda birinci s›kl›kta konjenital kalp hastal›klar›n›n ikinci s›rada da ro-matizmal kalp hastal›klar›n›n izlendi¤i tespit edilebilmifltir.Dolay›s› ile bu yaz›da ayr›nt›l› olarak bu konulara de¤inilmektedir. Gebeli¤in evre-lerine göre kapak velositelerinde oluflan de¤iflkenlikler Doppler ve renkli Doppler ekokardiyografi ile izlenebilmekte ve bu de¤iflkenlikler göz önüne al›narak kapaklardaki darl›k dereceleri oldukça do¤ru olarak de¤erlendirilebilmektedir. Do¤ru tan› do¤ru sa¤ kal›m de¤erlendir-mesine yol açacak ve hasta için seçilecek do¤ru tedaviyi yönlendirecektir.Tan›sal tetkikler aras›nda ionize radyasyona maruz kalman›n gebelerdeki olumsuz etkileri düflünüldü¤ünde ekokardiyografinin yeri daha da iyi anlafl›labilir. Ancak ekokardiyografinin gebelerde kul-lan›m›nda da ALARA prensibinin göz ard› edilmemesi gerekmektedir. (Anadolu Kardiyol Derg 2006; 6: 169-73)
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Annaahhttaarr kkeelliimmeelleerr:: Ekokardiyografi, Doppler, gebelik
ted uterus produce a further increase in CO. Most hemodynamic changes of pregnancy resolve by 2 weeks postpartum (2). The more recent use of Doppler cardiac output measurement techni-ques has greatly increased our understanding of the magnitude and timing of CO changes during pregnancy.
During pregnancy left ventricular mass increases by 52%. There is an increase in left ventricular diastolic and end-systolic diameters (12% and 20%, respectively), left ventricular posterior wall diameter during diastole and systole (22% and 13%, respectively) and left intraventricular septum during diasto-le and systodiasto-le (15% and 19%, respectively) (4) . The natural volu-me overload in pregnancy besides leading to a reversible 'physi-ological' left ventricular hypertrophy results as a short-term dec-rease in systolic function and a significant change in left ventri-cular diastolic function. Left ventriventri-cular diastolic function incre-ases in the first two trimesters but declines in the third trimester with a decrease in acceleration, consistent with an increase in ventricular compliance. Mitral valve A-wave maximum velocity increases during pregnancy by 19%, while mitral valve E-wave maximum velocity and the ratio of E-wave/A-wave velocities inc-reases early in pregnancy by about 14% and 6% respectively, with a subsequent decline to 4% and 10%, respectively, below non-pregnant levels (4). Changes in heart rate, preload, and contractility as well as stage of pregnancy influence this altera-tion (6). While left ventricular systolic funcaltera-tion is normal in all pa-tients one week after childbirth, left ventricular hypertrophy and left ventricular diastolic dysfunction persist for nearly two months (7).
Besides evaluating physiological alterations echocardiog-raphy provides information about disease etiology, accurate and noninvasive assessment of severity and means of monitoring progression. Women with congenital heart disease now compri-se the majority of pregnant women (2). The next largest group includes women with rheumatic heart disease. With the excep-tion of patients with Eisenmenger syndrome, severe surgical noncorrected cyanotic disease, severe pulmonary artery hyper-tension, pulmonary vascular obstructive disease and Marfan syndrome with aortopathy, maternal death during pregnancy in women with heart disease is rare. However, pregnant women with heart disease do remain at risk for other complications inc-luding heart failure, arrhythmia and stroke (2). Doppler echocar-diographic measurement of pulmonary pressures allows identifi-cation of women with pulmonary hypertension, quantitation of disease severity and evaluation of the respond to therapy with nifedipine or nitric oxide. The major limitation of Doppler data in this setting is that only pressures not vascular resistance can be assessed.
In Eisenmenger syndrome there may not be a tricuspid re-gurgitant jet so the presence of pulmonary hypertension must then be inferred from the findings of a large nonrestrictive intra-cardiac communication, a short time to peak velocity in the pul-monary artery, midsystolic notching on the pulmonic valve M Mode and the pattern of ventricular septal motion (8). There are conflicting reports about the estimation of pulmonary artery pressures (PAP) by echocardiography. Echocardiography was found to significantly overestimate PAPs compared with cathe-terization in pregnant patients with suspected pulmonary hyper-tension. Patients with structural cardiac defects appear to have a significantly greater difference in PAPs . Thirty-two percent of
pregnant patients with normal PAPs may be misclassified as ha-ving pulmonary artery hypertension when measured by echocar-diography alone as has been reported by Penning et al. (9), which should be kept in mind while using Doppler. Tetralogy of Fallot is the most common form of cyanotic congenital heart di-sease. In uncorrected or palliated pregnant patients with cyano-tic congenital heart disease the usual pregnancy associated fall in systemic vascular resistance and rise in CO exacerbate right to left shunting leading to increased maternal hypoxemia and cyanosis. Cyanotic congenital heart defects reported a high rate of maternal cardiac events (%32), prematurity (%37) and a low li-ve birth rate (%43). The lowest lili-ve birth rate (%12) was obserli-ved in those mothers with PaO2<85. Factors that predict a poor out-come include functional status before pregnancy, arterial oxy-gen saturation and blood hemoglobin. Maternal outcome is also strongly related to the degree of right ventricular pressure over-load (2) which can be estimated by echocardiography. Patients with Marfan syndrome and aortic root dilatation are at risk for aortic dissection and are difficult to manage. Thus serial echo-cardiography should be used to identify progressive aortic root dilatation (2). Patients who have cardiac decompensation or aor-tic dilatation > 40 mm are advised to avoid pregnancy (10).
The secundum atrial septal defect (ASD II) is, after bicuspid aortic valve, the second most frequent congenital heart disease. In the majority of patients the course of pregnancy is uncompli-cated, however, pregnancy-related cardiovascular changes may affect hemodynamic parameters of the defect An increase in the right ventricular and right atrial enlargement was found to be significantly greater in pregnant women with ASD II compa-red with healthy pregnant females. Also indirect parameters of the right ventricular strain (paradoxical systolic movement of the interventricular septum or tricuspid regurgitation) were more frequent in patients with ASD II rather than in controls. These al-terations were accompanied by a significant decrease in the me-an value of the Qp/Qs index which may suggest pregnme-ancy-rela- pregnancy-rela-ted favourable changes in the hemodynamic consequences of the defect - a decrease in the left-to-right shunt (11). Ventricular septal defect is also well tolerated except for an increased risk of endocarditis, and further evaluation of treatment is rarely ne-eded. Pregnancy does not significantly alter the ec-hocardiography findings. In patent ductus arteriosus (PDA) dias-tolic flow reversal in the pulmonary artery is seen with both co-lor flow imaging and pulsed wave Doppler. Left atrial or left vent-ricular (LV) enlargement in excess of the expected changes of pregnancy or of diastolic flow reversal in the descending thora-cic aorta should prompt evaluation of PDA (8).
The effect of increase in CO on the volume loaded right vent-ricle (ASD) or LV (VSD; PDA) is counterbalanced by the decrease in peripheral vascular resistance, making the evaluation of the shunt ratio problematic in borderline cases. However in the ab-sence of pulmonary hypertension, pregnancy, labour and deli-very are well tolerated; not necessitating accurate definition of the shunt ratio during pregnancy. Contrast echocardiography is not needed and should be avoided for detection of the interatrial shunt in pregnant women (8).
resis-tance promote transient right to left shunting (2). To prevent re-current cerebral embolism during pregnancy, delivery, and puer-perium, interventional closure of the patent foramen ovale can be performed without fluoroscopy under echocardiographic gu-idance (12).
There is an increase in the incidence of congenital heart di-sease among the offsprings of affected parents. Fetal echocar-diography, in combination with a multidisciplinary postnatal app-roach, can be used in the successful treatment of severe forms of congenital heart disease
Doppler and qualitative color Doppler are useful to illumina-te the pathophysiology of the hemodynamic consequences of fi-xed valve stenosis during pregnancy with respect to the labile nature of gradients resulting from variable loading conditions of pregnancy.
Mitral stenosis (MS) is the most common rheumatic valvular lesion encountered during pregnancy (2).
Although the hypervolemia and tachycardia may exacerbate mitral valve obstruction, echocardiographic measurement of mit-ral stenosis severity including 2D valve area, Doppler gradients and pressure half time valve area, remain valid in pregnancy allo-wing optimization of patient monitoring and therapy (8). Mean transvalvular gradient and PAP should be calculated during 3-5 months and thereafter with monthly follow-ups (13-14).
In some severe cases maternal or fetal complications may necessitate mechanical relief of stenosis severity preferably with balloon valvuloplasty which can safely be performed in the second trimester. Echocardiography is then valuable in asses-sing the likelihood of complications and the expected result of valvuloplasty. Transthoracic or transesophageal echocardiog-raphy (TEE) allows fluoroscopy time to be minimized (15). The mitral valve area (MVA), measured by the evaluation of the pres-sure half-time through an echo-Doppler-cardiogram, and the functional class before pregnancy, using the criteria of the New York Heart Association were found to be the most interesting predictor variables (16).
Operation should be reserved for those with symptoms ref-ractory to medical treatment and low output syndrome and sho-uld be delayed till the fetus is mature and if possible sectio befo-re MVR should be performed (17).
When aortic stenosis (AS) complicates pregnancy it is usu-ally because of congenital bicuspid aortic valve. Women with symptomatic AS should delay pregnancy until after surgical cor-rection. With severe AS, the limited ability to augment CO may result in abnormal elevation of LV systolic and filling pressures which in turn precipitate or exacerbate heart failure or ischemia. In addition the noncompliant, hypertrophied ventricle is sensitive to falls in preload (2). As stroke volume increases across the ste-notic valve with pregnancy, an increase in the pressure gradient measured by Doppler echocardiography is seen. However cal-culation of valve area with the continuity equation still provides accurate assessment of stenosis severity.
The role of echocardiography in AS is to accurately deline-ate disease severity so that monitoring and therapy during preg-nancy and in the peripartum period can be optimized (8).
Most pregnant women can be managed medically but ballo-on aortic valvuloplasty or valve replacement during pregnancy has been required in rare cases. Pulmonary autograft aortic val-ve replacement (AVR) (Ross procedure) reported favorable out-comes (18).
Doppler echocardiography was used as a pre-pregnancy predictor of outcome in women with moderate-to-severe aor-tic stenosis. The patient's hemodynamic measurements du-ring exercise before conception closely approximated those of the hemodynamic burden placed on her heart during preg-nancy (19).
Pregnancies with asymptomatic regurgitant lesions are bet-ter tolerated. Pregnancy may result in a decrease in regurgitant severity due to afterload reduction of decreased systemic vas-cular resistance but this effect may be counterbalanced by the hormonal and vascular changes of pregnancy. In patients with severe regurgitation, decreased systemic vascular resistance due to pregnancy can result in an apparent decrease in regurgi-tant severity and improvement in LV systolic function. In these patients surgery may be inappropriately delayed. Quantitation of regurgitant jet may be misleading but when decompensation oc-curs echocardiography can differentiate whether increased CO demands of pregnancy or worsening of the underlying valvular abnormality is the underlying reason (8). Repair of the valve sho-uld be preferred in those patients with severe cardiac insuffici-ency and aortic or mitral valve regurgitation.
Doppler evaluation of velocities, pressure gradients and thus pressure half time method across prosthetic valves is also influ-enced by alterations in loading conditions and increased heart rate and stroke volume so the volume flow rate should be taken into consideration when evaluating a prosthetic valve in nant women. Due to accelerated valve deterioration during preg-nancy the use of bioprostheses in women who need valvular he-art surgery before pregnancy necessitate later valve replace-ment again and perhaps an autograft or homograft can be an al-ternate approach (8-20). Key factors influencing successful co-urse of pregnancy and labour in patients with prosthetic valves are: adequate left ventricular function, properly functioning val-ves and effective anticoagulation (21).
Endocarditis prophylaxis is initiated at onset of active labor when indicated. AHA states that delivery by sectio and vaginal delivery in the absence of infection do not require endocardirtis prophylaxis, except perhaps in patients at high risk (2).
When a pregnant woman with mechanical heart valve requ-ires anticoagulation, heparin and warfarin are used but contro-versy continues as to which is better at different stages of preg-nancy. Oral anticoagulation with warfarin is better accepted by patients and is effective. However warfarin embryopathy may be produced during organogenesis and fetal intracranial bleeding can occur throughout pregnancy. A daily warfarin dose of <5 mg was associated with no cases of embryopathy. Fetal intracrani-al hemorrhage during vaginintracrani-al delivery is a risk with warfarin un-less it has been stopped at least 2 weeks before labor. Recent practice guidelines have favored use of warfarin and low dose aspirin either during the entire pregnancy or substituted by he-parin only during the peak teratogenic period (6-12th week of gestaton) (2).
One of the other applications of echocardiography is the eva-luation of changes due to hypertension during pregnancy. Preg-nancy induced hypertension is defined as an increase in systolic blood pressure (SBP) from baseline>30 mmHg, a diastolic blood pressure (DBP) increase>15 mmHg, SBP>140 mmHg or DBP>90 mmHg. Preeclampsia is defined as hypertension after the 20th week of pregnancy and proteinuria > 300 mg per 24 hrs (8).
Gestational hypertension (GH), which is noted in some preg-nancies during the third trimester and being considered a tempo-rary condition and essential hypertension (EH) induce similar early altered diastolic filling of the left ventricle. In one recent re-port left atrial function was found to be similar in GH and normal subjects (N) and lower than that in EH patients. Both GH and EH patients had early left ventricular diastolic filling pattern signifi-cantly different as compared to normal subjects (longer isovolu-metric relaxation time, deceleration time of the E wave, and lo-wer E wave velocity in GH and EH vs. N), whereas the late filling properties were similar in GH and normal subjects with a lower A velocity, and velocity-time integral vs. EH. Systolic fraction of the pulmonary vein flow was similar in GH and EH patients and lower in normal subjects. Altered left ventricular geometry was more common in GH than in EH, whereas normotensive subjects did not show any alteration of the geometric pattern in this re-port. Gestational hypertension was found to be characterized by altered left ventricular geometry, which was far less common during essential hypertension (24).
In preeclampsia the concept of a hyperdynamic disease mo-del with a subsequent hemodynamic crossover to low CO and high resistance circulation coinciding with the onset of the clini-cal syndrome has been reported. Women with gestational hyper-tension had no such hemodynamic crossovers and maintained hyperdynamic circulation throughout pregnancy (25). So, on the basis of these hemodynamic subsets, appropriate medical the-rapy can be chosen after Doppler CO measurements and calcu-lation of systemic vascular resistance in patients with preg-nancy-induced hypertension and preeclampsia (8).
In patients with hypertrophic cardiomyopathy maternal mor-tality is increased compared with the general population. Howe-ver, absolute maternal mortality is low and appears to be princi-pally confined to women at a particularly high risk (26). No echo-cardiographic or clinical feature is a useful indicator of preg-nancy related complications. However, rare complications can occur and therefore planned delivery and fetal monitoring are still required for some patients (27).
Peripartum cardiomyopathy (PPCM) is a rare cardiac complication and diagnosis includes clinical (development of cardiac failure in the last month of pregnancy or within 5 months after delivery, absence of an identifiable cause of car-diac failure and absence of recognizable heart disease prior to the last month of pregnancy) and echographic (left ventricular systolic dysfunction) criteria (28-29). Clinically, PPCM shows pulmonary symptoms such as dyspnea, tachypnea and coug-hing. It is possible to misdiagnose PPCM for pulmonary embo-lism (PE). As massive PE is the leading cause of maternal de-ath, it is the most feared diagnosis and PPCM can easily be for-gotten. However, distinguishing between the two is vital for the patient as management of PPCM is quite different from that of PE. Echocardiography is a valuable tool in the differential diag-nosis (30). Echocardiography can also provide prognostic in-formation in PPCM as patients who deteriorate have higher LV
end- diastolic diameters as compared to those who improve. It remains unclear whether pregnancy is safe in those with reco-very of systolic function. Dobutamine stress echocardiography may have a role in evaluating contractile reserve in women with recovered systolic function who are contemplating furt-her pregnancies, but tfurt-here are as yet insufficient data to con-firm the validity of this approach (2-31).
Hydropericardium is the most frequent form of pericardial in-volvement in pregnancy. Small amounts of fetal pericardial fluid (< 2 mm in echocardiography, in diastole) can be detected after 20 weeks of gestation. Larger effusions should raise clinical con-cern for hydrops fetalis, Rh disease, hypoalbuminemia, and in-fectious or autoimmune disorder. Pericardiocentesis should be performed only for very large effusions causing clinical signs of cardiac tamponade or if presence of suppurative, tuberculous or neoplastic pericardial effusion is suspected. Echocardiographic guidance of pericardiocentesis is preferred to fluoroscopic gu-idance in order to avoid fetal X-ray exposure (32).
The treatment of the pregnant patient with cardiac arrhyth-mias requires important modifications of the standard practice of arrhythmia management (2). Electrical cardioversion is safe in pregnancy (33) and implantable cardoverter defibrillators repor-ted favorable maternal and fetal outcomes (34). Echocardiograp-hic monitoring has a role during electrophysiological testing and pacemaker implantation by transesophageal echocardiographic guidance (35) can safely be performed when necessary.
As has been explained echocardiography can be used in pregnant women to illuminate many underlying pathologies. But 2 questions will arise.
The first is about the safety of echocardiography.
As very well known, diagnostic ultrasound has been used for many years with a remarkable history of safety during the stan-dard clinical practice. Introduction of color and pulsed Doppler modes resulted with higher levels of transmitted and absorbed ultrasonic energy which raised the question for the safety of its use in early pregnancy. Potential bioeffects of ultrasound energy can be categorized as thermal, or relating to increase in tempe-rature in the region of insonation, or mechanical, relating prima-rily to cavitation. However one of the advantages of echocardi-ographic monitoring during pregnancy is the avoidance of expo-sure to ionizing radiation. Although there are no strictly defined limits established for the use of Doppler ultrasound in the early pregnancy there is an unequivocal demand for carefulness that is best expressed by the ALARA principle,-as low as reasonably achievable (36).
And the second question is about whether all pregnant wo-men should undergo echocardiographic evaluation. The answer to this question is no. As expected the physiologic adaptation in pregnancy may result in flow murmurs, which are very common in pregnants and do not need echocardiographic exam. However murmurs with >3/6 grade, which also radiate to different locati-ons over the chest do need further evaluation. Also those pati-ents with cardiovascular symptoms of congestive heart failure and those with known preexisting heart disease require further echocardiographic follow-ups.
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